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Yellow_Cad
Joined: 02 Apr 2008
Posts: 151
Location: Sacramento, CA
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 Posted: Mon Jul 07, 2008 7:38 pm Post subject: |
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Well, I visited this Commando one more time and here is what I learned:
1) The stroke is that of an 850
2) All three numbers (plate, motor, and gearbox) all match (235565)
3) The number on the motor has a little round symbal before and after it and after the round symbal after it is the number 1 and then another little round symbal
4) There is smaller than normal (not much space at all) space between the top fin on the barrels and the lowest fin on the head
5) Many years ago this bike blew a head gasket. This was repaired but the silver paint on the head is very thick and almost certainly brushed on. This made me think that it might have been originally polished and painted during the repair. |
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Jeandr
Joined: 22 Jan 2008
Posts: 87
Location: Canada
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| Posted: Mon Jul 07, 2008 10:23 pm Post subject: Stolen?? |
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You could also be in the presence of a stolen bike renumbered for resale. My brother bouht a 750 Atlas and we later learned the serial numbers had been tampered with, kept quiet bout it then and sold it later. Even the police could not see the serial number had been changed when they started to add their own punces to keep bike theft down.
Jean |
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Yellow_Cad
Joined: 02 Apr 2008
Posts: 151
Location: Sacramento, CA
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| Posted: Tue Jul 08, 2008 8:07 am Post subject: |
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| L.A.B. and 79x100, please let me know what you think of my most recent findings on this bike especially the number 1 just after the serial number on the crankcase and the high compression part all coupled with the three matching 235,xxx serial number. As you have said, maybe just an odd numbered 850. |
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79x100
Joined: 19 May 2006
Posts: 689
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| Posted: Tue Jul 08, 2008 10:44 am Post subject: |
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I don't know. All the reference sources suggest that it is too high a number for the 200000 series 750 engines and yet also not correct for a 300000 series 850 motor.
The Vintage Motor Cycle Club in England have the surviving factory ledgers but there are odd gaps. I found neither my '72 750 nor '75 850 in the books which is strange because I know from the Registration records that both were UK market bikes with traceable histories and I do not recall any blocks of numbers out of sequence. Perhaps worth sending them an e-mail. I don't think it will bring anything to light though.
Has the owner let you take photographs of the numbers ? We could perhaps form a view as to whether this was an important (to us numbers nuts) discovery or if it looks to have been tampered with.
I am suspicious of the number 1 after the main ciphers. I have seen a quantity of pre-production cases and things showing casting oddities to back it up but they have never looked like proper production numbers.
The idea that it was an 850 number seems odd as that should not be before 300000 and not be higher than 325000 as the Mk111s started then.
If the frame paint is original, you should be able to see a number begining 'F' stamped beside the red plate and this may give a clue to where in the sequence it comes. |
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L.A.B.
Moderator
Joined: 20 Nov 2004
Posts: 1848
Location: Norfolk, UK
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| Posted: Tue Jul 08, 2008 1:00 pm Post subject: |
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| Yellow_Cad wrote: | | All three numbers (plate, motor, and gearbox) all match (235565) |
I really have no idea why this particular Commando has such an odd serial number, or why there is an extra "1"? As all three stamped numbers are the same, the engine has the (presumably genuine?) circle stamp limit markings, so it could have been produced as some sort of special, rather than it being any attempt to hide an original identity if there's no evidence of any over-stamping or metal being removed that would have obliterated any original stamps?
| Yellow_Cad wrote: | | 4) There is smaller than normal (not much space at all) space between the top fin on the barrels and the lowest fin on the head |
The head may have been skimmed then? Was there an "RH number on the head?
As 79x100 has suggested, it could be worth approaching the VMCC, or the UK NOC to see if anything is known about it, but many of the factory production records from 1973 onwards no longer exist, apparently. |
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Yellow_Cad
Joined: 02 Apr 2008
Posts: 151
Location: Sacramento, CA
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| Posted: Tue Jul 08, 2008 1:21 pm Post subject: |
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| I was a tooling machinist for a lot of years, I have stamped a lot of things and seen a lot of things stamped, and I don't have any doubts that these numbers were done by the factory. Out of curiousity, I will email the sources you suggest L.A.B. and send them the link to this post with a question from me to them. I'll let you know what I find out. |
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Ron L
Joined: 27 Feb 2004
Posts: 1101
Location: Ohio
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| Posted: Wed Jul 09, 2008 4:01 am Post subject: |
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It's sounding more and more like this could be a short stroke 750. I'm not sure measuring the stroke through the spark plug hole is very accurate due to the angle.
The short stroke should have an RH7 head which would have been milled to achieve 10:1 compression so would have a visibly smaller spacing between the last cylinder fin and the first head fin.
It also would be logical (can I use that word when speaking of Norton?) to have numbered them after the MkV 750 but of course prior to the 30xxxx series of the 850.
Les has the right idea. What is the RH designation on the head? |
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nortonspeed
Joined: 29 Jun 2008
Posts: 6
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| Posted: Wed Jul 09, 2008 1:20 pm Post subject: |
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| Unlike Ron L said there should not be a visibly smaller spacing between the last cylinder fin and the first head fin as the RH7 head isn't milled to achieve a higher compression. This is done by using high compression short-stroke Omega pistons with valve-cutaways. So if you can see (or feel) a cutaway through the sparkplughole you will know its not the regular flat piston crown of the standard engine. |
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Ron L
Joined: 27 Feb 2004
Posts: 1101
Location: Ohio
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| Posted: Wed Jul 09, 2008 6:54 pm Post subject: |
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| Quote: | | Unlike Ron L said there should not be a visibly smaller spacing between the last cylinder fin and the first head fin as the RH7 head isn't milled to achieve a higher compression |
Really? I had never heard that. I wonder then what is the difference in an RH7 head and an RH4?
I also was under the impression that Norton did not recommend domed pistons for compression increase due to poorer gas flow. |
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wrench
Joined: 22 Feb 2007
Posts: 153
Location: Pennsylvania, USA
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| Posted: Wed Jul 09, 2008 7:37 pm Post subject: |
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| Yellow_Cad wrote: | | I was a tooling machinist for a lot of years, I have stamped a lot of things and seen a lot of things stamped, and I don't have any doubts that these numbers were done by the factory. Out of curiousity, I will email the sources you suggest L.A.B. and send them the link to this post with a question from me to them. I'll let you know what I find out. |
Good thread here, just catching up.
Yellow_Cad, can you educate one just why you have no doubt the numbers were stamped by the factory? As a machinist you have a particularly valuable insight into the process. I ask because the bike I bought was sold as a earlier 750 model, but I later learned it had an 850 frame, most likely made in Italy. I don't think this is a particularly bad combination, but it was presented to me as otherwise. I've been wondering ever since if the engine stamping was tampered with and I'd like to know what to look for.
Cheers--
wrench |
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Yellow_Cad
Joined: 02 Apr 2008
Posts: 151
Location: Sacramento, CA
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| Posted: Wed Jul 09, 2008 9:49 pm Post subject: |
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Well Wrench, what I am saying is that I am talking to the current owner that has owned the bike since it was months old and his friend that he bought it from owned those few months. He has all of the paper work, etc to back that up. On this matter, I was born at night, it just wasn't last night. I see in this case no reason or attempt to deceive.
As to the numbers and my experience with stamping them, the numbers that are there (plate, gear box, and crankcase) and which all match have all the appearances of not being tampered with at all as was suggested earlier in this post. Yeah, the world really could be square but I am trying to convey to people on this board what I am seeing and what I believe to be the case. To add to that, I am not making any assumptions on the frame. My only concern is to sort out the identification of the three matching numbers on the plate, gearbox and motor. |
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Yellow_Cad
Joined: 02 Apr 2008
Posts: 151
Location: Sacramento, CA
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| Posted: Thu Jul 10, 2008 1:53 pm Post subject: |
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| Wrench, I didn't mean to come across defensive. At work, I had people questioning my direct observations. During the 1980s I built a product that we serial numbered. There would only be two ways of changing an actual number stamped into metal, either an unsophisticated attempt or a much more sophisticated attempt. They would both have their clues for the metal worker. |
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nortonspeed
Joined: 29 Jun 2008
Posts: 6
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| Posted: Thu Jul 10, 2008 2:48 pm Post subject: |
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To Ron L,
RH7 head difference: bigger inlet valves with thinner stem, reduced valve angle, squishbandless hemisphere to suit the high compression Omega pistons. Hard to find one nowadays! |
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Ron L
Joined: 27 Feb 2004
Posts: 1101
Location: Ohio
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| Posted: Fri Jul 11, 2008 3:42 am Post subject: |
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Nortonspeed,
Sounds like you have first hand experience with the shortstroke. Care to elaborate? |
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Yellow_Cad
Joined: 02 Apr 2008
Posts: 151
Location: Sacramento, CA
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| Posted: Fri Jul 11, 2008 9:39 am Post subject: |
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As to the original bike in question on this post, I think I have learned enough from all of you to take it full circle. I saw it again last night and checked the cylinder head designation and frame number. It is an RH10 head and the frame number is: mark (same as used on motor for an 850 - circle with two verticle lines through it) 850 mark F107752 mark. Based on the head designation and my measurement of the stroke, I am convinced that it is a standard 850. As to the unusual serial number (235XXX), I belive it is just as Les said, "another one of those unsolved Norton mysteries."
Thanks for all the input; I sure learned a lot. Too bad it didn't turn out to be something a little more interesting. |
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Norton Commando Forum by Corporate Pages Web hosting using phpbb
The Unapproachable Norton Commando
At the end of 1967 the Norton Commando was announced.
The Norton Commando was greeted with a certain amount of scepticism because on first sight the commando appeared to comprise of the old Norton Dominator twin cylinder engine mounted at an inclined angle in a set of new cylinder parts.
It was not realized that the new Norton Commando Isolastic method of engine suspension damped out all engine vibration and produced a machine which had uncanny smoothness for a vertical twin. In due course the critics were silenced and the Norton Commando had the distinction of being regarded as the first of todays so called superbikes. There can be little doubt that the original design concept of the Norton Commando has proved correct, since comparatively few modifications of any real consequence have been made since production commenced during 1968.
Now nearly 40 years later Norton Commando riders like us are a breed of our own, and as far as we are concerned its still more fun to go for a blat on the old Norton Commando, and fast. As a Norton Commando owner and enthusiast, my goal here is to promote and give credit to those who keep the Norton name going.
It is more deserving to give credit to the Commando itself, for after all these years it continues to be respected. The original Commando designers like John Favill are those who deserve the credit for developing this incredible motorcycle.
The Norton Commando Roadster and Interstate of the late seventies, never died. Although the Norton Villiers factory dispersed the tradition lived on. Today Kenny Dreer in the USA is developing the new 952 CC Norton. What a great looking bike this is, and its engineering is still based on the original layout. It will be interesting to see how the new 952CC Norton does in todays tough motorcycle market. One thing is for sure, I would own one if I could afford it.
